March 2017 Vol.5 No.2

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Original Research Article

Isolation of Plant growth-promoting Bacillus Strains with Biocontrol Activity In vitro

Venant Nihorimbere^*1 and Marc Ongena²

¹University of Burundi, Faculty of Agronomy and Bioengineering, 2 Avenue de l'UNESCO, Bujumbura-Burundi
²University of Liège, Gembloux Agro Bio Tech, 2 Passage des déportés, 5030 Gembloux Belgium

*Corresponding Author's Email: venant.nihorimbere@ub.edu.bi,
Tel.: +257 75 694 392

Accepted March 06, 2017

Abstract

Several species of Bacillus genus represent an important tools in the biocontrol with plant-growth promoting activities. There is need of more works in this regards of great importance. In the present study, we combined isolation and screening activities of Bacillus strains to deeply investigate their potential traits to suppress plant-pathogenic and to stimulate plant growth. Fourteen strains of Bacillus were isolated from arable soils along the vicinity of Rusizi river at Cibitoke province (North Western of Burundi). Eight isolates among them were screened for their highest ability to inhibit growth of some phytopathogenic fungi such as Botrytis cinerea, Aspergillus niger, Fusarium oxysporum and Cladosporium cucumerinium. These strains identification based on 16s r-RNA and gyrase-A gene sequence analyses showed that 75 % of the isolates belonged to Bacillus amyloliquefaciens and the remaining others were closely related to Bacillus mojavensis. Some Bacillus amyloliquefaciens strains isolated from that part of Rusizi arable soil had high spores' yield in flasks cultivation (2.2 x 109 and 2.5 x 109 spores/ml) and were more potent for inhibiting fungal growth compared to the commercialized biopesticide strain S499 of Bacillus. They produced protease and cellulase cell-wall degrading enzymes and the liquid chromatography-electrospray mass spectrometry analyses of their supernatants showed the presence of a wide variety of lipopeptides homologous i.e. fengycin (A and/or B) C-14 to C-20, iturin A C-14 to C-17 and surfactin C-12 to C-17. Interestingly, their mass spectrum was characterized by some additional peaks which may correspond to new fengycins types. These findings showed that the Bacillus newly isolated would be used further as bio-inoculants to improve plant health.

Keywords: Bacillus, isolation, screening, antagonism, biocontrol, lipopeptides, fungi